/*
 * Copyright (C) 2013 Google Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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#include "flutter/sky/engine/platform/graphics/DrawLooperBuilder.h"

#include "flutter/sky/engine/platform/geometry/FloatSize.h"
#include "flutter/sky/engine/platform/graphics/Color.h"
#include "flutter/sky/engine/platform/graphics/skia/SkiaUtils.h"
#include "flutter/sky/engine/wtf/RefPtr.h"
#include "third_party/skia/include/core/SkColor.h"
#include "third_party/skia/include/core/SkColorFilter.h"
#include "third_party/skia/include/core/SkDrawLooper.h"
#include "third_party/skia/include/core/SkPaint.h"
#include "third_party/skia/include/effects/SkBlurMaskFilter.h"

namespace blink {

DrawLooperBuilder::DrawLooperBuilder() {}

DrawLooperBuilder::~DrawLooperBuilder() {}

PassOwnPtr<DrawLooperBuilder> DrawLooperBuilder::create() {
  return adoptPtr(new DrawLooperBuilder);
}

sk_sp<SkDrawLooper> DrawLooperBuilder::detachDrawLooper() {
  return m_skDrawLooperBuilder.detach();
}

void DrawLooperBuilder::addUnmodifiedContent() {
  SkLayerDrawLooper::LayerInfo info;
  m_skDrawLooperBuilder.addLayerOnTop(info);
}

// This replicates the old skia behavior when it used to take radius for blur.
// Now it takes sigma.
static SkScalar RadiusToSigma(SkScalar radius) {
  SkASSERT(radius > 0);
  return 0.57735f * radius + 0.5f;
}

void DrawLooperBuilder::addShadow(const FloatSize& offset,
                                  float blur,
                                  const Color& color,
                                  ShadowTransformMode shadowTransformMode,
                                  ShadowAlphaMode shadowAlphaMode) {
  // Detect when there's no effective shadow.
  if (!color.alpha())
    return;

  SkColor skColor = color.rgb();

  SkLayerDrawLooper::LayerInfo info;

  switch (shadowAlphaMode) {
    case ShadowRespectsAlpha:
      info.fColorMode = SkBlendMode::kDst;
      break;
    case ShadowIgnoresAlpha:
      info.fColorMode = SkBlendMode::kSrc;
      break;
    default:
      ASSERT_NOT_REACHED();
  }

  if (blur)
    info.fPaintBits |= SkLayerDrawLooper::kMaskFilter_Bit;  // our blur
  info.fPaintBits |= SkLayerDrawLooper::kColorFilter_Bit;
  info.fOffset.set(offset.width(), offset.height());
  info.fPostTranslate = (shadowTransformMode == ShadowIgnoresTransforms);

  SkPaint* paint = m_skDrawLooperBuilder.addLayerOnTop(info);

  if (blur) {
    const SkScalar sigma = RadiusToSigma(blur / 2);
    uint32_t mfFlags = SkBlurMaskFilter::kHighQuality_BlurFlag;
    if (shadowTransformMode == ShadowIgnoresTransforms)
      mfFlags |= SkBlurMaskFilter::kIgnoreTransform_BlurFlag;
    paint->setMaskFilter(
        SkBlurMaskFilter::Make(kNormal_SkBlurStyle, sigma, mfFlags));
  }

  paint->setColorFilter(
      SkColorFilter::MakeModeFilter(skColor, SkBlendMode::kSrcIn));
}

}  // namespace blink
